Certain machines operate in environments and work with materials that may subject machine components to substantial abrasion. As a result, various components of these machines incur high rates of abrasive wear. Examples of such machines include, mining machines, excavating machines and other machines that move and handle rock, ore, earth, and various abrasive materials associated with mining and excavating. These machines commonly have buckets and/or other implements that break, dig, and handle material. Ground engaging tools (GET) are components that are usually added to buckets and implements in order to enhance their effectiveness. GET generally occupy areas on buckets and other implements that are exposed to the greatest abrasive forces and thus greatest wear. For example, GET may include such components as adapters for tips, cutting edges for buckets, edge protectors for buckets, sidebar protectors for buckets, tips for buckets, shrouds for cutting edges, and variously formed wear members. GET are commonly (but not always) replaceable components that take most of the severe abrasion and wear associated with these buckets and implements.
The materials encountered by the above mentioned machines not only present challenges in terms of abrasion, but also may subject GET to high impact stresses. In addition to being abrasive, material that is engaged by these machines during mining, excavating, or handling operations is not always of uniform consistency and density. Large masses of earth and rock may be encountered and engaged during machine operation, and GET may be subjected to higher strain rates than would occur in working with material of relatively uniform consistency and density. Accordingly, while wear resistance is a desired GET characteristic of major advantage because of the abrasive nature of the material involved, it is not the only desired characteristic. The possibility of encountering material that may place great stress on GET, frequently with sudden impact, makes toughness and the ability to survive high strain rates without breaking additional desirable characteristics.
It would be both beneficial and desirable to provide a steel with a composition that exhibits both high wear resistance and high impact strength and that could be employed in manufacturing GET. It also would be desirable and beneficial that steel with such a composition further increase in strength and wear resistance by tending to wear by deformation rather than by chipping, or removal of material. Such a steel would enable the manufacture of cast GET components with extended life relative to those in the current GET industry, and result in significant savings in cost and maintenance time.
One type of manganese steel purported to increase wear resistance is disclosed in U.S. Pat. No. 4,612,067 that issued on Sep. 16, 1986 to Larson et al. (“the '067 patent”). The '067 patent discloses an austenitic (Hadfield) manganese steel containing about 25% manganese, 1.4% carbon, and 0.1 to 1% silicon, with the balance being essentially iron. The '067 patent discloses a desire to avoid intentional addition of molybdenum and posits the view that its tendency to be a strong carbide forming element may detract from work hardenability and cause brittle failure. The '067 patent also contemplates aluminum only as a deoxidizer rather than a substantive additional element to the alloy, and essentially characterizes aluminum as an impurity to be avoided.
Although the alloy steel disclosed in the '067 patent may provide improved wear resistance and toughness, still further improvements in manufacturing costs and material characteristics may be possible. In particular, the '067 patent discloses a purposeful omission of molybdenum and does not recognize the advantages of added molybdenum for its desirable characteristics, or that any carbides that may form as a consequence of added molybdenum can be dissolved and dispersed into the austenitic microstructure during reheating of a cast object. In addition, the '067 patent does not recognize that aluminum can be added in an amount sufficient to be consequential to weight reduction without substantially affecting wear resistance and toughness.
The high manganese steel with enhanced wear and impact characteristics of the present disclosure solves one or more of the problems set forth above and/or other problems of the prior art.